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Time-lapse of the Lower North Fork Fire

Posted On: April 3, 2012 - By: Curtis Seaman

On 26 March 2012, strong winds, high temperatures and low humidities re-ignited embers from a controlled burn that took place the previous week near Conifer, CO. The Lower North Fork fire quickly spread in the high winds, eventually burning more than 4000 acres and damaging or destroying 27 homes. Three people were killed, presumably because they were unable to evacuate before their homes were engulfed in flame. One family’s daring escape from the fire was caught on a cell phone camera and made national news (CAUTION: strong language has not been edited out). Many interesting pictures of the fire may be found here, here, and here.

Channel I-4 of VIIRS (centered at 3.74 µm) captured the hot spot from the Lower North Fork fire on each of Suomi-NPP’s afternoon (ascending) overpasses last week. These images make up the loop shown below.

5-day loop of I-4 images of the Lower North Fork fire

5-day loop of afternoon I-4 images of the Lower North Fork fire

In this image loop, the color scale represents observed brightness temperature such that warmer pixels appear darker and cooler pixels appear lighter. Pixels warmer than 330 K appear black, and pixels colder than 250 K appear white. The time between each image in the loop is approximately 24 hours.

The first image in the loop, taken at 20:24 UTC on the 26th, captured the hot spot shortly after the fire was first reported. The hot spot as seen by I-4 expanded significantly during the first 24 hours, before lighter winds and firefighting efforts greatly limited the growth of the fire. Over the last three frames, the hot spot can be seen to cool and shrink slightly.

Low (liquid) clouds can be seen as dark splotches on the images from the 28th and 29th of March, which should not be confused with fires. This is due to the fact that liquid clouds are highly reflective at 3.7 µm, and the reflection of solar radiation during the day increases the observed brightness temperature, so they appear darker. The persistently bright sideways “C” shape to the northeast of the fire is Chatfield Reservoir, which has a low brightness temperature due to the low water temperature in the reservoir and the relatively low emissivity of liquid water at this wavelength. Cherry Creek Reservoir (to the northeast of Chatfield Reservoir) and Marston Lake (to the north of Chatfield Reservoir) can also be seen.

With clear skies, the burn area shows up quite clearly in the I-band false color RGB composite of I-1, I-2 and I-3, taken at 20:06 UTC 27 March 2012 – the same time as the second frame of the loop above.

RGB composite of VIIRS channels I-1, I-2 and I-3 of the Lower North Fork fire, 20:06 UTC 27 March 2012

RGB composite of VIIRS channels I-1, I-2 and I-3 of the Lower North Fork fire, 20:06 UTC 27 March 2012

The burn area shows up as a sizeable dark brown spot in the forests (which show up as green) southwest of Denver.

After the driest and warmest March on record in Denver, hopefully this is not the start of a long, devastating fire season (link goes to PDF file).